JPH0899622A - Antiskid braking device for vehicle - Google Patents

Abstract

PURPOSE: To acquire braking performance and driving stability during split-road driving and/or turning driving, by select-low controlling a pressure of brake liquid for rear wheels under normal conditions or by select-high controlling it in case of a split road and correcting a threshold for the select-high control so as to lessen a lock to some extent. CONSTITUTION: A brake control system 15 is equipped with first and second channels to control the left and right front wheels 1, 2 respectively and a third channel to control the rear wheels 3, 4. The third channel is changed from a select-low control over to a select-high control and its control threshold is corrected so as to lessen a lock to some extent when the road is judged to be split by a split-road judging measure. Thus, braking performance is secured by keeping high a braking force for the rear wheel on the higher-μside of the road and yet driving stability is ensured by controlling a lock of the rear wheel on the low-μ side of the road through the correction to lessen lock to some extent.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an antiskid brake device for a vehicle, which is capable of ensuring braking performance and steering stability during split road traveling and / or turning traveling.

[0002]

2. Description of the Related Art Conventionally, various anti-skid brake devices for controlling a brake fluid pressure based on a vehicle speed and a wheel speed have been put into practical use in order to suppress the locking of the wheel during braking of the vehicle and ensure the braking performance. Has been done. In this anti-skid brake system, the brake fluid pressure for the front wheels is divided into two systems, left and right, and the brake fluid pressure for the rear wheels is integrated left and right.
A control valve for controlling hydraulic pressure (pressure increasing valve and pressure reducing valve) is provided in the brake hydraulic system that is controlled by two independent systems, right and left, so that the slip ratio of the wheels reaches the target value via the control valve. The brake fluid pressure is adjusted, but it is common to repeat a predetermined pattern of pressure increase, pressure increase hold, pressure decrease / pressure decrease hold for a plurality of cycles, or a predetermined pattern of pressure increase and pressure decrease for a plurality of cycles. Target. The following μ means the friction coefficient of the road surface.

Here, the brake fluid pressure of the rear wheels is generally controlled by select low control for the front wheels (the brake fluid pressure is controlled in accordance with the wheel having a low wheel speed, that is, the wheel on the low μ side). However, various anti-skid controls have been proposed in order to improve braking performance and steering stability when traveling on a split road where only one side of the road surface is a high μ road. For example, in Japanese Patent Laid-Open No. 1-269655,
When driving on a uniform road, the left and right brake fluid pressures are controlled independently, and the rear wheel brake fluid pressure is controlled by select low control.On the other hand, when driving on a split road, contrary to the above, the front wheel brake fluid pressure is controlled. There is described an anti-skid brake device in which the selection low control is performed under a predetermined condition and the brake hydraulic pressure of the rear wheels is controlled independently.

Japanese Unexamined Patent Publication No. 6-56018 has a four-wheel independent brake fluid pressure system, and when running on a uniform road, any one of a plurality of controls including select low control and independent control is disclosed. On the other hand, there is described an anti-skid control device that is controlled by an independent limiting control that limits the increasing tendency of the braking force of the other wheel according to the wheel with large slip while traveling on a split road. By the way, conventionally, no technology has been proposed as a technique for improving the anti-skid control during turning or the anti-skid control during turning on a split road.

[0005]

When the brake fluid pressure of the rear wheels is controlled by the select low control for the front wheels, the anti-skid control (ABS control) of the front wheels on the low μ road side is started during traveling on the split road. Then, the ABS control of the brake fluid pressure of the rear wheels is also started, the brake fluid pressure is reduced to suppress the lock of the rear wheels, and the braking force of the brake device of the rear wheels is extremely reduced. However, one side of the road surface is a high μ road, there is no risk of the rear wheels on the high μ road side locking, and the braking force of the rear wheels is fully exerted even though there is sufficient margin. I can't.

On the other hand, when turning at a relatively high speed,
When the wheel load on the turning inner wheel decreases and the vehicle tends to lock during braking, ABS control of the front wheel on the turning inner wheel side is started, and ABS control of the brake fluid pressure on the rear wheel is started by the select low control. As in the case of traveling, although the braking force of the rear wheels has a sufficient margin, the braking force cannot be fully exerted. An object of the present invention is to provide an anti-skid brake device for a vehicle that can ensure braking performance and steering stability during traveling on a split road and / or during turning traveling.

[0007]

According to a first aspect of the present invention, there is provided a wheel speed detecting means for detecting a rotational speed of a wheel, a brake fluid pressure for the left and right front wheels, and a brake fluid pressure for the left and right rear wheels. In an anti-skid brake device for a vehicle, which is equipped with a hydraulic pressure adjusting means for integrally adjusting the hydraulic pressure and an anti-skid control means for controlling the hydraulic pressure adjusting means based on the wheel speed detected by the wheel speed detecting means, Is provided with a split road determining means for determining whether or not the road is a split road, and the anti-skid control means normally performs a select low control of the brake fluid pressure of the rear wheels, and the split road determining means determines that the road is a split road. Occasionally, the brake fluid pressure of the rear wheels is configured to be controlled to select high, and the anti-skid control means controls the brake fluid pressure of the rear wheels to select high. It is provided with a correction means for correcting the control threshold in the lock shallow.

According to a second aspect of the present invention, an antiskid brake device for a vehicle having the same precondition as the first aspect is provided with a turning determination means for determining turning of the vehicle, and the antiskid control means is normally operated. The brake fluid pressure of the rear wheels is controlled to select low, and when the turning determination means determines that the vehicle is turning, the brake fluid pressure of the rear wheels is controlled to select high. Compensation means for compensating the control threshold value when the brake hydraulic pressure is controlled to the select high control is provided in a shallow lock state.

According to a third aspect of the present invention, in an anti-skid brake device for a vehicle having the same precondition as in the first aspect, split road determination means for determining whether or not the traveling road surface is a split road, and determination for turning of the vehicle. The anti-skid control means normally controls the brake fluid pressure of the rear wheels to select low, and the split road determination means determines that it is a split road and the turn determination means determines that the vehicle is turning. When it is determined that there is a brake fluid pressure of the rear wheel is configured to select high control,
The antiskid control means is provided with a correction means for correcting the control threshold value when the brake hydraulic pressure of the rear wheel is controlled to select high to a shallow lock.

According to a fourth aspect of the present invention, in a vehicle anti-skid brake device having the same precondition as in the first aspect, split road determining means for determining whether or not the traveling road surface is a split road is provided, and the anti-skid control means is , Is configured to control the brake fluid pressure of the rear wheels with select low,
The anti-skid control means is provided with a correction means for correcting the control threshold value for controlling the brake fluid pressure of the rear wheels to the lock depth when the split road determination means determines that the split road is a split road.

According to a fifth aspect of the present invention, an antiskid brake device for a vehicle having the same precondition as in the first aspect is provided with a turning determination means for determining turning of the vehicle, and the antiskid control means is for the rear wheel. It is configured to control the brake fluid pressure to select low, and when the anti-skid control means determines that the turning determination means is turning, the control threshold value for controlling the brake fluid pressure of the rear wheels is corrected to a deeper lock. The correction means is provided.

According to a sixth aspect of the present invention, in an anti-skid brake device for a vehicle having the same precondition as in the first aspect, split road determination means for determining whether or not the traveling road surface is a split road, and determination for turning of the vehicle. The anti-skid control means is configured to control the brake fluid pressure of the rear wheels to select low, and the anti-skid control means determines that the split road determination means is a split road and turns. When the determination means determines that the vehicle is turning, a correction means for correcting the control threshold value for controlling the brake fluid pressure of the rear wheels to a deeper lock is provided.

[0013]

According to the present invention, the wheel speed detecting means detects the rotational speed of the wheel, the hydraulic pressure adjusting means independently adjusts the brake hydraulic pressure of the left and right front wheels, and the left and right rear wheels. The brake fluid pressure of is integrated and adjusted. The anti-skid control means controls the hydraulic pressure adjusting means based on the wheel speed detected by the wheel speed detecting means. The split road determination means determines whether or not the traveling road surface is a split road, and the anti-skid control means controls the brake fluid pressure of the rear wheels normally under the select low condition. Select high control. The correction unit corrects the control threshold value when the select high control is applied to the brake fluid pressure of the rear wheel so that the control threshold value is set to a shallow lock (a slight decrease in brake fluid pressure).

As described above, since the brake fluid pressure of the rear wheels is selectively high-controlled during traveling on a split road, even if the anti-skid control is started for one front wheel, the anti-skid control for the rear wheels is not started. Since the brake fluid pressure of the rear wheels is not reduced, the braking force of the rear wheels on the high μ road side can be maintained high and the braking performance can be secured. Moreover, the correction threshold corrects the control threshold when the brake hydraulic pressure of the rear wheels is controlled to select high, so that the locking of the rear wheels on the low μ road side can be suppressed and steering stability can be ensured.

In the invention of claim 2, the operation of the precondition is the same as that of claim 1, but the turning determination means determines whether the vehicle is turning, and the anti-skid control means normally brakes the rear wheels. Select low control of hydraulic pressure, and select high control of brake hydraulic pressure of rear wheels when turning. The correction means corrects the control threshold value when the brake hydraulic pressure of the rear wheel is controlled to select high to a shallow lock. During turning, since the wheel load of the turning inner wheel is reduced, the anti-skid control for the front wheel on the turning inner wheel side can be easily started.

However, as described above, when the vehicle is turning, the brake fluid pressure of the rear wheels is controlled to be select high.
Even if the anti-skid control is started for the front wheel on the inside of the turning side, the anti-skid control for the rear wheels is not started and the brake fluid pressure for the rear wheels is not reduced. It can be maintained and the braking performance can be secured.
Moreover, the correction threshold corrects the control threshold when the brake hydraulic pressure of the rear wheels is controlled to select high, so that the locking of the rear wheels on the low μ road side can be suppressed and steering stability can be ensured.

In the invention of claim 3, the operation of the precondition is the same as that of claim 1. The split road determination means determines whether or not the road is a split road, the turn determination means determines whether or not the vehicle is turning, and the anti-skid control means normally performs a select low control of the brake fluid pressure of the rear wheels to travel the split road. At times, the brake fluid pressure of the rear wheels is controlled to select high. The correction means corrects the control threshold value when the brake hydraulic pressure of the rear wheel is controlled to select high to a shallow lock. As is clear from the description in claims 1 and 2, when the vehicle travels on a split road, the braking performance can be secured by controlling the select hydraulic pressure of the brake fluid of the rear wheels, and the control threshold value can be set. Steering stability can be secured by correcting the lock shallower.

In the invention of claim 4, the operation of the precondition is the same as that of claim 1. The split road determination means determines whether or not the traveling road surface is a split road, the anti-skid control means constantly controls the brake fluid pressure of the rear wheels by the select low control, and the correction means controls it while traveling on the split road. Correct the threshold value to a deeper lock (like increasing the brake fluid pressure). In this way, by constantly controlling the brake fluid pressure of the rear wheels by the select low control, the locking of the rear wheels can be suppressed and the steering stability can be ensured. Moreover, while traveling on the split road, by correcting the control threshold value to the lock depth, the brake fluid pressure of the rear wheels is corrected to the higher direction to suppress the pressure reduction,
Braking performance can be secured.

In the invention of claim 5, the operation of the precondition is the same as that of claim 1. The turning determination means determines whether the vehicle is turning, the anti-skid control means always controls the brake fluid pressure of the rear wheels by the select low control, and the correction means locks the control threshold deeper during turning. to correct. In this way, by controlling the brake fluid pressure of the rear wheels by the select low control, the locking of the rear wheels can be suppressed and the steering stability can be ensured even when the wheel load of the turning inner wheels is reduced during turning. Moreover, by correcting the control threshold value to the lock depth during turning, it is possible to correct the brake fluid pressure of the rear wheels in the upward direction to suppress the pressure reduction and to secure the braking performance.

In the invention of claim 6, the operation of the precondition is the same as that of claim 1. The split road determination means determines whether the traveling road surface is a split road, and the turning determination means determines whether the vehicle is turning. The anti-skid control means is
The brake fluid pressure of the rear wheels is always controlled by select low control,
The correction means corrects the control threshold value to a lock depth when turning on the split road. Claims 4 and 5
As is clear from the description, the steering stability can be secured by controlling the brake fluid pressure of the rear wheels by the select low control when the vehicle travels on a split road. Moreover, when the vehicle travels on a split road, the control threshold value is corrected to be deeper in the lock state, so that the brake fluid pressure of the rear wheels is corrected in the upward direction to suppress the pressure reduction and the braking performance can be secured.

[0021]

Embodiments of the present invention will be described below with reference to the drawings. First, the brake system of this vehicle will be described. As shown in FIG. 1, in the vehicle according to this embodiment, the left and right front wheels 1 and 2 are driven wheels, and the left and right rear wheels 3 and 4 are drive wheels, and the output torque of the engine 5 is the automatic transmission 6.
Is transmitted to the left and right rear wheels 3 and 4 via the propeller shaft 7, the differential device 8 and the left and right drive shafts 9 and 10. Each of the wheels 1 to 4 is a brake device 11 including discs 11a to 14a that rotate integrally with the wheels and calipers 11b to 14b that receive the supply of braking pressure and brake the rotation of the discs 11a to 14a.
14 are provided respectively, and these brake devices 11 to 14 are provided.
There is provided a brake control system 15 for operating the.

The brake control system 15 includes a booster 17 for increasing the stepping force on the brake pedal 16 by the driver, and a master silling 18 for generating a braking pressure according to the stepping force increased by the booster 17. Have and. The front wheel braking pressure supply line 19 from the master shilling 18 is branched into two paths, and the front wheel branching braking pressure lines 19a and 19b are respectively connected to the calipers 11a and 12a of the brake devices 11 and 12 of the left and right front wheels 1 and 2. The braking pressure line 19a connected to the brake device 11 for the left front wheel 1 is provided with a first valve unit 20 including an electromagnetic pressure increasing valve 20a and an electromagnetic pressure reducing valve 20b. The braking pressure line 19b leading to the brake device 12 is also provided with a second valve unit 21 including an electromagnetic pressure increasing valve 21a and an electromagnetic pressure reducing valve 21b.

On the other hand, in the rear wheel braking pressure supply line 22 from the master cylinder 18, an electromagnetic pressure increasing valve 23a,
Third valve unit 2 including electromagnetic pressure reducing valve 23b
3 is provided. This rear wheel braking pressure supply line 22
Is branched into two paths downstream of the third valve unit 23, and these rear wheel branch braking pressure lines 22a and 22b are respectively applied to the calipers 13b and 14b of the brake devices 13 and 14 of the left and right rear wheels 3 and 4, respectively. It is connected. The brake control system 15 variably controls the braking pressure of the brake device 11 for the left front wheel 1 via the first valve unit 20.
A channel, a second channel for variably controlling the braking pressure of the brake device 12 for the right front wheel 2 via the second valve unit 21, and both brake devices 13 for the left and right rear wheels 3, 4 via the third valve unit 23. , 14 and a third channel for variably controlling the braking pressure, and these first to third channels are controlled independently of each other.

The brake control system 15 includes a first
An ABS control unit 24 for controlling the third channel is provided. The ABS control unit 24 includes a brake signal from a brake switch 25 for detecting ON / OFF of the brake pedal 16 and a steering angle sensor for detecting a steering angle of the steering wheel. In response to the steering angle signals from the wheel speed sensors 26 and the wheel speed signals from the wheel speed sensors 27 to 30 that detect the rotational speeds of the four wheels 1 to 4, respectively, braking pressure control signals corresponding to these signals Anti-skid brake control (hereinafter referred to as ABS control) for suppressing locking and skid of the left and right front wheels 1 and 2 and rear wheels 3 and 4 by outputting to the third valve units 20, 21 and 23, respectively, for each channel. First to third
All channels are set to run in parallel.

The ABS control unit 24 includes pressure increasing valves 20a, 21a, 23a, which are duty solenoid valves in the first to third valve units 20, 21, 23, based on the wheel speeds detected by the wheel speed sensors 27-30. Pressure reducing valves 20b, 21b, 23 composed of duty solenoid valves
By controlling b and duty control, the front wheels 1 and 2 and the rear wheels 3 and 3 are controlled by the braking pressure according to the slip state.
The braking force is applied to No. 4. Each pressure reducing valve 2 in the first to third valve units 20, 21, 23
The brake oil discharged from 0b, 21b, 23b is supplied to the master cylinder 1 via a drain line (not shown).
8 is returned to the reservoir tank 18a.

In the ABS non-controlled state, no braking pressure control signal is output from the ABS control unit 24, the pressure reducing valves 20b, 21b and 23b are closed and held as shown, and the pressure increasing valves 20a, 21a and 23a are held. Are held open, the braking pressure generated in the master cylinder 18 in accordance with the depression force of the brake pedal 16 is applied to the brake device 11
To 14 and the braking forces corresponding to these braking pressures are directly applied to the front wheels 1 and 2 and the rear wheels 3 and 4.

The ABS control unit 24 is supplied with the detection signals of the wheel speed sensors 27 to 30, the steering angle sensor 26, the brake switch 25, etc., and the ABS control unit 24 is supplied with sensors and switches. Waveform shaping circuit that shapes the detection signal of the detection signal as required, A / D converter that performs AD conversion of various detection signals as required, input / output interface, microcomputer, drive for pressure increasing valve and pressure reducing valve It is composed of a circuit, a plurality of timers, etc., and the ROM of the microcomputer stores in advance control programs for antiskid brake control and various controls associated therewith, tables, maps, etc., and the RAM is provided with various work memories. Has been.

Next, an outline of the ABS control will be described. The wheel speeds V1 to V1 detected by the wheel speed sensors 27 to 30 are described.
Decelerations DV1 to DV4 and acceleration for each wheel based on V4
AV1 to AV4 are calculated respectively. In this case, the difference between the previous value of the wheel speed and the current value is divided by the sampling period Δt (for example, 8 ms), and the result is converted into gravity acceleration to be updated as the current acceleration or deceleration.

Further, it is determined whether or not the traveling road surface is a bad road by a predetermined bad road determination process. In this case, the number of times that the wheel acceleration or the wheel deceleration of the driven wheels 1 and 2 exceeds a predetermined rough road determination threshold value during a predetermined period is counted, and when the number of times is a predetermined value or less, the rough road flag is counted. Set Fak to 0,
When the number of times is larger than a predetermined value, the bad road flag Fak
Is set to 1. Although the ABS control is executed for each channel, the wheel speed of each wheel and the road surface friction state value Mu for each channel are calculated, and the pseudo vehicle speed Vr common to the three channels is calculated using these data. It In the present embodiment, the slip ratio of each wheel is calculated by slip ratio = (wheel speed / pseudo vehicle speed Vr) × 100, so the vehicle speed Vr
The larger the deviation of the wheel speed from, the smaller the slip ratio, and the greater the tendency of the wheel to slip.

Next, the main routine of the anti-skid brake control for each channel will be described with reference to the flow chart of FIG. 2 by taking the control for the first channel as an example.
2, 3, ...) Show each step. It should be noted that this main routine is a process executed every predetermined minute time (for example, 8 ms). First, various signals (brake SW signal,
The wheel speed V1) is read (S1), then it is determined whether the brake switch 25 is ON (S2), and the determination is No.
When, the brake is returned and the brake switch 25 is turned on.
In this case, the road surface friction state value Mu is calculated (S3), the pseudo vehicle body speed Vr is then calculated (S4), the control threshold value is set (S5), and the control signal output process is then executed. (S6), and then returns.

Calculation of road surface friction state value Mu ... FIG. 3
Reference First, various signals (flag Fabs, wheel speed V1) are read (S10), and then it is determined whether the flag Fabs is 1 (S11). This flag Fabs is set to 1 when any of the lock flags Flok1 to Flok3 of the first to third channels is 1, and when the determination in S11 is No, the road surface friction state value Mu is high. Mu = indicating frictional state
It is set to 3 (S12), and then the process returns. When the flag Fabs is 1, the deceleration DV of the left front wheel 1 is -20G.
It is determined whether or not it is smaller (S13), and when the determination is Yes, it is determined whether or not the acceleration AV of the left front wheel 1 is larger than 10 G (S14). If the determination is that acceleration AV ≦ 10 G, the road surface friction state is determined. The value Mu is Mu = 1 indicating a low friction state.
Is set (S15), and then the process returns.

When the deceleration DV <-20G or the acceleration AV> 10G, it is determined whether or not the acceleration AV> 20G (S16). If the determination is Yes, the road surface friction state value Mu is high friction state. Is set to Mu = 3 (S
17) and then return. When the determination in S16 is No, the road surface friction state value Mu indicates the medium friction state Mu.
= 2 is set (S18), and then the process returns. As described above, the road surface frictional state value Mu for the first channel is estimated at small time intervals based on the acceleration / deceleration of the wheel speed V1 and stored in the memory while being updated.
The road surface frictional state values are similarly estimated for the second and third channels, but the road surface frictional state values for the first to third channels will be referred to as Mu (1), Mu (2), and Mu (3 ).

Calculation processing of pseudo vehicle body speed Vr ... See FIGS. 4 and 5. Next, the calculation processing of the pseudo vehicle body speed Vr of the first channel will be described. First, various signals (wheel speeds V1 to V1) will be described.
4. Friction state values Mu (1), Mu (2), Mu (3) and the previous vehicle speed Vr) are read (S20), and then the wheel speed V1
~ The maximum wheel speed Vwm is calculated from V4 (S21),
Next, the maximum wheel speed change amount ΔVwm per sampling cycle Δt of the maximum wheel speed Vwm is calculated (S22). Next, from the map shown in FIG. 5, the frictional state values Mu (Mu (1), Mu
(2), the vehicle speed correction value Cvr corresponding to Mu (3) is read (S23), and it is then determined whether the maximum wheel speed change amount ΔVwm is equal to or less than the vehicle speed correction value Cvr. (S2
4).

As a result of the determination, when it is determined that the wheel speed change amount ΔVwm is equal to or less than the vehicle body speed correction value Cvr, the vehicle body speed Vr.
The value obtained by subtracting the vehicle speed correction value Cvr from the previous value of is replaced with the current value (S25). Therefore, the vehicle body speed Vr decreases at a predetermined gradient according to the vehicle body speed correction value Cvr.
On the other hand, when the wheel speed change amount ΔVwm is larger than the vehicle body speed correction value Cvr (when the maximum wheel speed Vwm shows an excessive change), the value obtained by subtracting the maximum wheel speed Vwm from the pseudo vehicle body speed Vr is the predetermined value V0. It is determined whether or not the above (S26).

That is, it is determined whether or not there is a large difference between the maximum wheel speed Vwm and the vehicle body speed Vr. If there is a large difference, the process proceeds to S25, and the maximum wheel speed Vwm and the vehicle body speed Vr are also compared. When there is no large gap between them, the maximum wheel speed Vwm is replaced with the vehicle body speed Vr (S27). In this way, the pseudo vehicle body speed Vr of the vehicle is updated every moment according to the wheel speeds V1 to V4. The calculation of the pseudo vehicle body speed Vr is a common calculation process for the first to third channels.

Control threshold setting process ... FIGS. 6 to 10
Reference Next, the control threshold value setting process will be described with reference to FIGS. 6 to 10. First, various signals (vehicle speed Vr, friction state values Mu (1), Mu (2), Mu (3), flag Fak,
The steering angle θ) is read (S30). Next, in S31, as shown in FIG. 8, the friction state value Mu is obtained from the table TB1 using the vehicle speed range, the road surface friction state value Mu, and the rough road flag Fak as parameters. A running condition parameter corresponding to the vehicle speed Vr is selected, and various control threshold values corresponding to the selected running condition parameter are set based on the table TB2 in FIG. 9 and stored in the work memory.

However, the friction state values Mu applied to the table TB1 of FIG. 8 are the friction state values Mu (1) to Mu (3).
Of the friction state value Mu is 1
At this time, when the vehicle speed Vr is in the medium speed range, the traveling state parameter LM2 is selected. On the other hand, the rough road flag Fak = 1
When the vehicle is on a rough road, as shown in FIG.
A driving state parameter corresponding to r is selected. That is, when traveling on a rough road, the wheel speed fluctuates greatly and the road surface friction coefficient tends to be estimated to be small.

Here, as shown in table TB2, as various control threshold values, a 1-2 intermediate deceleration threshold value B12 for switching from phase I to phase II in FIG. 14 and phase II to phase III. 2 for switching to
-3 Intermediate slip rate threshold value Bsg, 3-5 Intermediate deceleration threshold value B for determination of switching from phase III to phase V
35, 5-1 for judging switching from phase V to phase I
The slip ratio threshold Bsz and the like are set for each running state parameter.

The deceleration threshold value, which greatly affects the braking force, becomes 0 G as the friction state value Mu decreases in order to achieve both the braking performance in the high friction state and the responsiveness in the low friction state. It is set to approach. Table T
In the example of B2, when the traveling state parameter is LM2, 1
-2 intermediate deceleration threshold B12, 2-3 intermediate slip ratio threshold Bsg, 3-5 intermediate deceleration threshold B35, 5-1 slip ratio threshold Bsz, -0.5G, 90% , 0
G and 90% are read out respectively.

Next, the frictional state value Mu (here, Mu =
It is determined whether Mu (1)) is 3 (S32), the process proceeds to S34 if No, and the bad road flag Fak is 0 if Yes.
It is determined whether or not (S33). When the rough road flag Fak = 0, the absolute value of the steering angle θ detected by the steering angle sensor 93 is 90.
It is determined whether or not it is less than ° (S34), and the absolute value of the steering angle θ ≧ 9
When the angle is 0 °, the control threshold value correction process according to the steering angle θ is performed (S35). The control threshold correction processing is performed by the control threshold correction table (table T shown in FIG. 10).
It is executed based on B3), and the process proceeds to S38.

In the table TB3 of FIG. 10, the 2-3 intermediate slip ratio threshold is set in order to secure the steerability when the road is not bad with low friction, medium friction and high friction and the steering wheel operation amount is large. The value obtained by adding 5% to the value Bsg and the 5-1 slip ratio threshold value Bsz is set as the final threshold value, and the other threshold values are set as they are as the final threshold value. In the case of a bad road with a high friction (flag Fak = 1), in order to ensure the running performance when the steering wheel operation amount is small, 2-3 intermediate slip ratio threshold value Bsg
And the value obtained by subtracting 5% from the 5-1 slip ratio threshold value Bsz is set as the final threshold value. next,
If the determination in S34 is Yes, each control threshold is set as it is as a control threshold, and the process proceeds to S38.

On the other hand, when it is determined in S33 that the rough road flag Fak = 1, the table T of FIG. 10 is determined in S36.
Based on the rough road flag Fak and the steering angle θ, B3 is set to 5% from the 2-3 intermediate slip ratio threshold value Bsg and the 5-1 slip ratio threshold value Bsz only when the steering angle θ <90 °. The correction process of setting the subtracted value as the control threshold value is executed, and then, in S37, the value obtained by subtracting 1.0 G from the 1-2 intermediate deceleration threshold value B12 is controlled based on the table TB3. Perform the correction process to set as the threshold value, and
The process moves from 37 to S38. The correction in S37 is for delaying the control responsiveness and ensuring a good braking force because the wheel speed sensors 27 to 30 are likely to make erroneous detections on a bad road.

Next, step S38 is a step that is not executed by the ABS control of the first and second channels, but is executed only by the ABS control of the third channel. In the ABS control of the third channel, this S38 is executed. A control threshold value correction process for ensuring braking performance and steering stability during traveling on a split road is executed, and then the process returns. FIG. 7 shows the subroutine of this control threshold value correction processing.
Describing with reference to FIG. 11, in FIG. 7, first, various signals (brake switch signal, road surface friction state value Mu
(1), Mu (2)) are read (S40), and then it is determined whether the brake switch 25 is ON (S41).
When it is F, the routine returns, but when it is ON, in S42 the running road surface is a split road (one side of the road surface has a high μ
On the road, the other side of the road is not a high μ road) or the friction state value M
The determination is made based on u (1) and Mu (2), and the third channel is set to the select high control and the correct low control depending on whether the road is a split road or not.

If it is a split road, in S44, the third channel is switched from the select low control to the select high control, and the control threshold value is set based on the control threshold value correction table (table TB4) in FIG. Is corrected to a shallow lock (on the side where the brake fluid pressure drops), and then the process returns. The select high control is a control that starts the ABS control of the third channel when the ABS control of both the first channel and the second channel is started (when both the lock flags Flok1 and Flok2 become 1). The select low control is the ABS control of the third channel when the ABS control of either the first channel or the second channel is started (when one of the lock flags Flok1 and Flok2 becomes 1). This control is started, and the third channel is set to the select low control during normal times other than when traveling on the split road.

The table TB4 in FIG. 11 is a table for correcting the 2-3 intermediate slip ratio threshold Bsg and the 5-1 slip ratio threshold Bsz of the control thresholds by 5%. If the 2-3 intermediate slip ratio threshold value Bsg is largely corrected, the decompression start time is advanced, so the lock is corrected shallowly, and if the 5-1 slip ratio threshold value Bsz is largely corrected, the pressure increase start time is delayed. Therefore, the lock becomes shallow. However, 2-3 intermediate slip ratio threshold value Bsg and 5-
The table TB4 may be configured to largely correct only one of the 1-slip-rate thresholds Bsz. on the other hand,
If the determination in S42 is No, in S45, the third channel is maintained in the select low control, and the process returns without correcting the control threshold value.

Control signal output process ... See FIGS. 12 to 14. Next, a control signal output process of setting a phase by various control threshold values and outputting a braking control signal of each phase to the pressure increasing valve or the pressure reducing valve. The first channel will be described as an example with reference to the flowcharts of FIGS. 12 and 13. First, various signals required for the following arithmetic processing are read (S50), and then the brake switch 25 is turned on.
It is judged whether or not it is N (S51), and if the judgment is No, S
When the vehicle returns from 52 and the brake switch 25 is ON, the vehicle speed Vr is a predetermined value C1 (for example, 5.0 Km / H).
Below, and the wheel speed V1 is a predetermined value (eg 7.5 Km / H)
It is determined whether or not the following (S53). If the determination in S53 is Yes, the vehicle is sufficiently decelerated, and there is no need for ABS control, so the process returns via S52, but the determination in S53 is
If No, the process proceeds to S54.

At S52, the phase flag P1, the lock flag Flok1, and the continuation flag Fcn1 are reset to 0, respectively, and then the process returns. Next, in S54, it is determined whether or not the lock flag Flok1 is 0, and if the flag Flok1 is 0 before the ABS control is started, the process proceeds to S55 to determine the wheel speed V1.
Deceleration DV1 (provided that DV1 ≦ 0) is a predetermined value D0
(Eg, -3G) or less is determined, and the determination is Yes
If so, the process proceeds to S56. On the other hand, the determination in S54 is No.
If so, the process proceeds to S59.

Next, if the determination in S55 is Yes, the lock flag Flok1 is set to 1 (S66), then the flag P1 is set to 2 and the phase II (holding phase after pressure increase) is entered ( (S57), then a braking control signal preset for phase II is output to the pressure increasing valve 20a and the pressure reducing valve 20b (S58), and then the process returns. In this case, the pressure increasing valve 20a and the pressure reducing valve 20b are kept closed (duty ratio = 0).

After the ABS control is started, since the flag Flok1 = 1, the process proceeds from S54 to S59 and the flag P1 is set to 2
It is determined whether or not (S59), and when the flag P1 = 2, S6.
If the flag P1 = 2 is not satisfied, the process proceeds to S63. In S60, it is determined whether or not the slip ratio S1 is equal to or less than the 2-3 intermediate slip ratio threshold Bsg.
However, if the slip ratio S1 ≦ threshold value Bsg is reached by repeating the above steps, the flag P1 is set to 3 in S61 subsequent to S60 and the phase III (pressure reduction phase) is executed. ).

Next, in S62, a braking control signal preset for phase III is output to the pressure increasing valve 20a and the pressure reducing valve 20b, and then the process returns. Phase II
At I, the booster valve 20 is closed (duty ratio =
0) and the pressure reducing valve 20b is driven at a predetermined duty ratio. If the flag P1 is not 2 in the determination of S59, it is determined in S63 following S59 whether the flag P1 is 3 or not, and if the flag P1 = 3, S6.
4. If the determination in S63 is No, the process proceeds to S67.

Next, in S64, it is determined whether or not the deceleration DV1 is equal to the 3-5 intermediate deceleration threshold value B35, and it is determined as No at the beginning, so the process proceeds from S64 to S62. When the deceleration DV1 = the threshold value B35 is repeated, the flag P1 is set to 5 in S65, and the phase V (post-reduction pressure holding phase) is entered. Next, in S66, a braking control signal preset for phase V is output to the pressure increasing valve 20a and the pressure reducing valve 20b, and then the process returns. In this case, booster valve 2
0a and the pressure reducing valve 20b are kept closed.
Next, if the determination in S63 is No, it is determined in S67 whether or not the flag P1 = 5, and if the flag P1 = 5, S is determined.
68, and if the flag P1 = 5 is not satisfied, S7
Go to 4. When the flag P1 = 5, it is determined whether the slip ratio S1 is 5-1 slip ratio threshold value Bsz or more (S68).

Since it is determined to be No at the beginning, S6
The process from 8 to S66 is repeated. In phase V, the slip ratio S1 increases and the determination in S68 is Yes.
When s is reached, in S69, the flag P1 is set to 1 and the phase I (pressure increase phase) is entered, and the continuation flag Fcn1 is set to 1. Next, in S70, the timer T1 that counts the elapsed time after the start of the phase I is reset and then started, and then in S71, it is determined whether or not the count time T1 of the timer T1 is less than or equal to a preset rapid pressure increase time Tpz. If the rapid pressure increase time Tpz is the first time or less, the process proceeds from S71 to S72 and S72.
In the above, the braking control signal set in advance for the initial rapid pressure increase of phase I is the pressure increasing valve 20a and the pressure reducing valve 20b.
Output, and then returns. In this case, the pressure increasing valve 20a is driven at a predetermined duty ratio, and the pressure reducing valve 20b is kept closed.

Next, after the shift to phase I, the determination in S67 is No, so the flow shifts from S67 to S74, and
At 74, it is determined whether the flag P1 = 1, and the flag P1
= 1, the deceleration DV1 is 1-2 in S75.
It is determined whether or not the intermediate deceleration threshold value B12 or less. Since the determination is No at the beginning, the process proceeds from S75 to S71, and from S71 to S72 before the rapid pressure increase time Tpz elapses. repeat. While repeating this, when the rapid pressure increase time Tpz elapses after shifting to the phase I, S71
Since the determination of No is No, the process proceeds from S71 to S73, and the braking control signal set in advance for the gradual pressure increase of Phase I is output to the pressure increasing valve 20a and the pressure reducing valve 20b.
After that, it repeats returning. In this case, the pressure increasing valve 20a is driven at a predetermined duty ratio, and the pressure reducing valve 20b is kept closed.

Next, when the determination in S75 is Yes, S7
In step 6, the flag P1 is set to 2, and then S58.
Move to. Thus, after the start of ABS control, the phase
II, Phase III, Phase V, Phase I, Phase
II, phase III, ... Are executed in this order over a plurality of cycles, and when the determination in S53 is Yes or the brake switch 25 is OFF, a series of ABS control ends (see FIG. 14). . The ABS control described above has been described by taking the ABS control of the brake device 11 for the left front wheel 1 as an example, but the ABS control is also executed in parallel for the other brake devices 12 to 14.

Next, the operation of the ABS control described above will be described with reference to FIG. 14 by taking the brake device 11 for the left front wheel 1 as an example.
Will be described with reference to. In the ABS control non-execution state during deceleration, when the brake fluid pressure generated by the depression operation of the brake pedal 25 is gradually increased and the rate of change of the wheel speed V1 (deceleration DV1) reaches -3G, the lock flag is set. Flok1 is set to 1, and the ABS control is substantially started from the time ta. In the first cycle immediately after the start of the control, the frictional state value Mu is set to 3 (high frictional state), and various control threshold values are set according to the traveling state parameter.

Next, the slip ratio S1 of the front wheels 1 and the wheel deceleration DV1 are compared with various control threshold values, the phase is changed from phase 0 to phase II, and the brake fluid pressure is increased to the level after the pressure increase. Held in. When the slip ratio S1 falls below the 2-3 intermediate slip ratio threshold Bsg, the phase II
To phase III (pressure reduction phase), the brake fluid pressure is reduced at a predetermined gradient from time tb, and the rotational force of the front wheels 1 begins to recover. When the wheel deceleration DV1 further decreases to the threshold value B35 (0G) after depressurization, the phase shifts from phase III to phase V (holding phase after depressurization), and from that time tc, the brake fluid pressure becomes the level after depressurization. Retained.

When the slip ratio S1 becomes equal to or higher than the 5-1 slip ratio threshold value Bsz in this phase V, the continuation flag Fcnl is set to 1 and the ABS control shifts from the time td to the second cycle. At this time, the brake fluid pressure is forcibly shifted to phase I (pressure increase phase), and immediately after the shift to phase I, the brake fluid pressure is increased steeply for a preset rapid pressure increase time Tpz. After the pressure is applied, the brake fluid pressure gradually increases with a gentler gradient. Thus
Immediately after the shift to the second cycle, the brake fluid pressure is reliably increased and a good braking pressure is secured.

On the other hand, after the second cycle, the appropriate frictional state value Mu is determined, and various control threshold values corresponding to the running state parameters determined by the frictional state value Mu and the vehicle body speed Vr are set in tables TB2 and TB3. Since it is set based on, the precise control of the brake fluid pressure is performed according to the running state. After that, in the phase V in the second cycle, when the slip ratio S1 is larger than the threshold value Bsz, the phase I of the third cycle is entered.

Here, in the ABS control of the present application, as described with reference to FIGS. 7 and 11, the third channel is switched from the select low control to the select high control during traveling on the split road, and the third channel is selected based on the table TB4. Correct the control threshold for the channel to a shallow lock. In this way, by switching from the select low control to the select high control, the ABS control start timing of the third channel is delayed, the brake fluid pressure is maintained high, and the braking force of the brake device for the high μ side driving wheel is reduced. It is possible to prevent and secure braking performance. However, in this case, there is a high possibility that the low-μ side drive wheel will be locked, so by correcting the control threshold value to a shallower lock as described above, the low-μ side drive wheel and the high-μ side drive wheel will be locked. Locking can be prevented and steering stability can be ensured.

Next, a description will be given of a plurality of modification modes in which the control threshold value correction process of FIG. 7 of the above embodiment is modified.
The same steps will be denoted by the same reference symbols and redundant description will be omitted.

1] As shown in FIG. 15, for the bridge determined to be a split road in S42, it is determined whether or not the vehicle is turning based on the steering wheel steering angle detected by the steering angle sensor 26 in S43. Then, when the determination is Yes, in S44, the third channel is switched to the select high control, and the control threshold value is corrected to the lock shallow.
When turning, the ABS control of the channel of the front wheel on the turning inner wheel side is likely to start due to the reduction of the wheel load of the turning inner wheel, but if the third channel is maintained in the select low control, the ABS control of the third channel also starts. As a result, the brake fluid pressure is reduced, and the braking performance may deteriorate. However, as described above, when turning on the split road,
By switching the channel to the select high control and correcting the control threshold value to a shallow lock, it is possible to secure braking performance and steering stability.

2] As shown in FIG. 16, the split road determination step of S42 is omitted, and during the turning traveling, the third channel is switched to the select high control and the control threshold is determined in S44 based on the determination of S43. Correct the value to a shallow lock. That is, as described above, during turning, although the ABS control of the channel of the front wheel on the inner turning wheel side is likely to start due to the reduction of the wheel load on the inner turning wheel, the third channel is switched to the select high control to set the control threshold value. By correcting the lock shallower, braking performance can be secured and steering stability can be secured.

3] As shown in FIG. 17, when the vehicle is traveling on the split road through the determination in S42, the third routine is performed in S46.
The channel is maintained in the select low control, the control threshold value is corrected to the lock depth, and then the process returns. In this case, the 2-3 intermediate slip ratio threshold Bsg and the 5-1 slip ratio threshold Bsz are corrected to 5% smaller based on the table TB5 of FIG. 2-3 If the intermediate slip ratio threshold value Bsg is corrected to a small value, the decompression start timing will be delayed, resulting in a deeper lock, and 5-1 slip ratio threshold value B
If sz is corrected to a small value, the pressure increase start time will be earlier and the lock will be deeper.

However, 2-3 intermediate slip ratio threshold value Bsg
The table TB5 may be configured such that only one of the 5-1 and the slip ratio threshold value Bsz is corrected to be smaller.
If it is not the split road, the third road is determined in S47.
The channel is maintained in the select low control, and the control threshold value is not corrected, and the process returns. As described above, when the third channel is maintained in the select low control while traveling on the split road, the ABS control of the third channel is started early and the locking of the rear wheels 3 and 4 is suppressed to secure the steering stability. it can. Moreover, by correcting the control threshold value to a deeper lock (on the higher brake fluid pressure side), it is possible to suppress a decrease in the braking force of the braking device for the drive wheel on the high μ side and ensure braking performance.

4] As shown in FIG. 19, S42 and S4
Based on the judgment of 3, when the vehicle travels on a split road, S
At 46, the third channel is maintained in the select low control, the control threshold value is corrected to the lock depth, and then the process returns. When turning on a split road, ABS control of the first channel or the second channel is easily started, and if the third channel is maintained in the select low control,
The ABS control of the third channel is started early and the locking of the rear wheels 3 and 4 can be suppressed to ensure the steering stability.
By correcting the control threshold value to the lock depth, it is possible to suppress the decrease in the braking force of the brake device for the driving wheel on the high μ side and to secure the braking performance.

5] As shown in FIG. 20, when the determination of the split road is omitted and it is determined that the vehicle is turning through the determination of S43, the third channel is maintained in the select low control and the control threshold is determined in S46. Correct the value to a deeper lock and return. As described above, when turning, the ABS control of the first channel or the second channel is easily started, and the lock of the rear wheels 3 and 4 is suppressed by maintaining the third channel in the select low control. It is possible to secure steering stability. Then, by correcting the control threshold value to the lock depth, it is possible to suppress the decrease in the braking force of the braking device for the driving wheel on the high μ side and to secure the braking performance.

6] In the ABS control of the above-described embodiment, the cycle consisting of four phases of pressure increase, pressure increase maintenance, pressure reduction, and pressure reduction maintenance is repeated, but a cycle consisting of two phases of pressure increase and pressure reduction. AB that repeats
You may comprise in S control. The road surface friction estimation processing, the pseudo vehicle speed calculation processing, and the like in the above embodiments are merely examples, and the calculation may be performed by various methods other than this, and the split road is determined by the left and right pressure reducing valves. 20b, 2
You may make it determine from the integrated value etc. of the decompression time of 1b. It is needless to say that the present invention can be implemented in a mode in which various modifications are added without departing from the spirit of the present invention.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an anti-skid brake device for a vehicle according to an embodiment of the present invention.

FIG. 2 is a flowchart of a main routine of anti-skid brake control.

FIG. 3 is a flowchart of a subroutine for calculating a road friction state value.

FIG. 4 is a flowchart of a subroutine of a pseudo vehicle body speed calculation process.

FIG. 5 is a diagram of a map of vehicle body speed correction values.

FIG. 6 is a flowchart of a subroutine of control threshold value setting processing.

FIG. 7 is a flowchart of a subroutine of control threshold value correction processing in S38 of FIG.

FIG. 8 is a chart of a table in which running state parameters are set.

FIG. 9 is a chart of a table in which various control threshold values are set.

FIG. 10 is a chart of a control threshold correction table.

FIG. 11 is a chart of a control threshold correction value table.

FIG. 12 is a part of a flowchart of a control signal output processing subroutine.

FIG. 13 is the rest of the flowchart of the control signal output processing subroutine.

FIG. 14 is an operation time chart of anti-skid brake control.

FIG. 15 is a flowchart of a subroutine of control threshold value correction processing in a modified mode.

FIG. 16 is a flowchart of a subroutine of control threshold value correction processing in a modified mode.

FIG. 17 is a flowchart of a subroutine of control threshold value correction processing in a modified mode.

18 is a chart of a control threshold value correction value table used for the correction process of FIG.

FIG. 19 is a flowchart of a subroutine of control threshold value correction processing in a modified mode.

FIG. 20 is a flowchart of a subroutine of control threshold value correction processing in a modified mode.

[Explanation of symbols]

 1, 2 front wheels (driven wheels) 3, 4 rear wheels (driving wheels) 11-14 braking device 15 braking system 24 ABS control unit 26 steering angle sensor 27-30 wheel speed sensor

Claims (6)

[Claims] 1. Wheel speed detection means for detecting the rotational speed of a wheel, and hydraulic pressure adjustment means for independently adjusting the brake fluid pressures of the left and right front wheels and integrally adjusting the brake fluid pressures of the left and right rear wheels. In a vehicle anti-skid brake device having an anti-skid control means for controlling the hydraulic pressure adjusting means based on the wheel speed detected by the wheel speed detecting means, a split road judgment for judging whether or not the traveling road surface is a split road The anti-skid control means normally controls the rear wheel brake fluid pressure to select low, and the split road determination means determines the rear wheel brake fluid pressure to select high. The anti-skid control means is configured to control, and the control threshold for controlling the select hydraulic pressure of the brake fluid of the rear wheels is supplemented with a shallow lock. An anti-skid brake device for a vehicle, which is provided with a correcting means for correcting it. 2. Wheel speed detection means for detecting the rotational speed of the wheels, and hydraulic pressure adjustment means for independently adjusting the brake fluid pressures of the left and right front wheels and integrally adjusting the brake fluid pressures of the left and right rear wheels. In an anti-skid brake device for a vehicle, which includes an anti-skid control means for controlling the hydraulic pressure adjusting means based on the wheel speed detected by the wheel speed detecting means, a turning judging means for judging turning running of the vehicle is provided, The anti-skid control means is configured to normally control the brake fluid pressure of the rear wheels to select low, and to control the brake fluid pressure of the rear wheels to select high when the turning determination means determines that the vehicle is turning. The anti-skid control means is provided with a correction means for correcting the control threshold when the brake fluid pressure of the rear wheel is controlled to select high to a lock shallower. Anti-skid brake system for vehicles. 3. Wheel speed detection means for detecting the rotational speed of the wheels, and hydraulic pressure adjustment means for independently adjusting the brake fluid pressures of the left and right front wheels and integrally adjusting the brake fluid pressures of the left and right rear wheels. In a vehicle anti-skid brake device having an anti-skid control means for controlling the hydraulic pressure adjusting means based on the wheel speed detected by the wheel speed detecting means, a split road judgment for judging whether or not the traveling road surface is a split road Means and a turn determination means for determining turning of the vehicle, wherein the anti-skid control means normally controls the brake fluid pressure of the rear wheels to select low, and the split road determination means is a split road. When it is determined and the turning determination means determines that the vehicle is turning, the brake fluid pressure of the rear wheels is configured to be selected high, and the anti-skid control is performed. An anti-skid brake device for a vehicle, characterized in that the means is provided with a correcting means for correcting the control threshold value when the brake hydraulic pressure of the rear wheels is subjected to the select high control to a lock shallow. 4. Wheel speed detection means for detecting the rotational speed of the wheels, and hydraulic pressure adjustment means for independently adjusting the brake fluid pressures of the left and right front wheels and integrally adjusting the brake fluid pressures of the left and right rear wheels. In a vehicle anti-skid brake device having an anti-skid control means for controlling the hydraulic pressure adjusting means based on the wheel speed detected by the wheel speed detecting means, a split road judgment for judging whether or not the traveling road surface is a split road Means is provided, the anti-skid control means is configured to select low control the brake fluid pressure of the rear wheels, the anti-skid control means, when the split road determination means determines that the split road, the rear wheel An anti-skid brake device for a vehicle, comprising: a correction unit that corrects a control threshold value for controlling the brake fluid pressure of the vehicle to a lock depth. 5. Wheel speed detection means for detecting the rotational speed of the wheels, and hydraulic pressure adjustment means for independently adjusting the brake fluid pressures of the left and right front wheels and integrally adjusting the brake fluid pressures of the left and right rear wheels. In an anti-skid brake device for a vehicle, which includes an anti-skid control means for controlling the hydraulic pressure adjusting means based on the wheel speed detected by the wheel speed detecting means, a turning judging means for judging turning running of the vehicle is provided, The anti-skid control means is configured to control the brake fluid pressure of the rear wheels to select low, and when the turning determination means determines that the vehicle is turning, the anti-skid control means determines the brake fluid pressure of the rear wheels. An anti-skid brake device for a vehicle, comprising a correction means for correcting a control threshold value to be controlled to a lock depth. 6. Wheel speed detection means for detecting the rotational speed of the wheels, and hydraulic pressure adjustment means for independently adjusting the brake fluid pressures of the left and right front wheels and integrally adjusting the brake fluid pressures of the left and right rear wheels. In a vehicle anti-skid brake device having an anti-skid control means for controlling the hydraulic pressure adjusting means based on the wheel speed detected by the wheel speed detecting means, a split road judgment for judging whether or not the traveling road surface is a split road Means and turning determination means for determining turning of the vehicle are provided, the anti-skid control means is configured to select low control the brake fluid pressure of the rear wheels, the anti-skid control means, the split road determination When the means determines that the vehicle is on the split road and the turning determination means determines that the vehicle is turning, the control threshold value for controlling the brake fluid pressure of the rear wheels is set to the lock depth. An anti-skid brake device for a vehicle, which is provided with a correction means for making a correction.